Effect of Selected Monoterpenes on Methane Oxidation, Denitrification, and Aerobic Metabolism by Bacteria in Pure Culture

Abstract

Selected monoterpenes inhibited methane oxidation by methanotrophs (Methylosinus trichosporium OB3b, Methylobacter luteus), denitrification by environmental isolates, and aerobic metabolism by several heterotrophic pure cultures. Inhibition occurred to various extents and was transient. Complete inhibition of methane oxidation by Methylosinus trichosporium OB3b with 1.1 mM (−)-α-pinene lasted for more than 2 days with a culture of optical density of 0.05 before activity resumed. Inhibition was greater under conditions under which particulate methane monooxygenase was expressed. No apparent consumption or conversion of monoterpenes by methanotrophs was detected by gas chromatography, and the reason that transient inhibition occurs is not clear. Aerobic metabolism by several heterotrophs was much less sensitive than methanotrophy was;Escherichia coli (optical density, 0.01), for example, was not affected by up to 7.3 mM (−)-α-pinene. The degree of inhibition was monoterpene and species dependent. Denitrification by isolates from a polluted sediment was not inhibited by 3.7 mM (−)-α-pinene, γ-terpinene, or β-myrcene, whereas 50 to 100% inhibition was observed for isolates from a temperate swamp soil. The inhibitory effect of monoterpenes on methane oxidation was greatest with unsaturated, cyclic hydrocarbon forms [e.g., (−)-α-pinene, (S)-(−)-limonene, (R)-(+)-limonene, and γ-terpinene]. Lower levels of inhibition occurred with oxide and alcohol derivatives [(R)-(+)-limonene oxide, α-pinene oxide, linalool, α-terpineol] and a noncyclic hydrocarbon (β-myrcene). Isomers of pinene inhibited activity to different extents. Given their natural sources, monoterpenes may be significant factors affecting bacterial activities in nature.

Spatial micro-distribution of methanotrophic activity along a 120-year afforestation chronosequence

“…Adamsen and King, 1993;Bradford et al, 2001). Also, methanotrophic activity can be inhibited by monoterpenes (Amaral et al, 1998) and organic acids (Wieczorek et al, 2011), processes which may be more important in the organic layer of mature forest stands. Oxidation rates of atmospheric CH 4 generally are limited by diffusion rates due to the low CH 4 concentrations; a downward shift of activity thus would tend to decrease soil CH 4 uptake rates.…”

“…Very likely, this pattern can be attributed to diffusion limitations (Hojberg et al, 1994). On the other hand, locations towards the aggregate core would protect methanotrophs from adverse biotic and abiotic effects such as protozoan grazing, drought stress, freeze-thaw events, and possibly also chemical inhibition by organic compounds such as terpenes (Amaral et al, 1998). Such adverse effects could be important given the oligotrophic nature of methanotrophs in low CH 4 environments which implies a low resilience after disturbance.…”

Evaluation of antibacterial effects and phytochemical screening of the aqueous and methanolic extracts of Hibiscus diversifolius

“…Terpenoids are terpenes to which additional elements such as oxygen have been added (Cowan, 1999). Terpenes and terpenoids have been found to possess antimicrobial activity (Mendoza et al, 1997;Amara et al, 1998). The mechanism of action of terpenes on microbes is not yet fully understood, but it is speculated to involve membrane disruption by the lipophilic compounds (Mendoza et al, 1997).…”

The role of terpenes in carbon and nitrogen cycling in boreal forest soils

“…Monoterpenes are the main components of plant volatile essential oils, and especially high concentrations are found in conifers (Amaral 1998). The most abundant monoterpenes in Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L) resin are α-pinene and β-pinene.…”